Method for improving the adhesion of organopolysiloxanes to solid surfaces



Patented June 30, 195 3 UNITED smras 2,643,964 METHOD FOR IMPROVING THE- ADHESION OF ORGANOPOLYSILOXANES TO SURFACES SOLID Robert Sinith Joha'n'nsen, Schenect dy; N; Y, signor to General Electric Company, a comers:

tion of New York No Drawin Application ember 14, 1950, Serial No. 190,241

32 Claims. 1

This invention is concerned with improving the adhesion of silicone rubbers to solid surfaces. More particularly, the invention relates to a process for improving the adhesion to'a solid surface of an organopolysiloxane convertible, e. g., by heat, to the solid, elastic state and containing less than 0.2 mol per cent copolymerized mono-' organosiloxane, e. g., monomethylsiloxane, which process comprises (1) treating the said surface with a composition comprising a hydrolyzable organosilicate compound corresponding to thegeneral formula:

R o Ro n- R t R where R and R are eacha member selected from the class consisting of alkyl groups and halogenated alkyl groups, and R, in addition is a member selected from the class consisting of aryl, aralliyl, alkaryl, alkoxy, aryloxy groups, and halogenated derivatives of the aforesaid aryl, aralkyl, alkaryl, alkoxy, and aryloxy groups, (2) effecting hydrolysis of the above-deposited silicate either in situ by virtue of the presence of hydrolysisinducing agents in the hydrolyaable silicate compound, or by external means, and (3) thereafter applying to the said treated surface the organepolysiloxane convertible to a cured, solid, elastic, organopolysiloxane. R in the above formula may be the same or different alkylgroups, and R and R. jn'a'y also be the same or different alkyl groups;

One of the objects of "this'invention is to improve the adhesion of certain silicone rubbers to various surfaces so as to give a bond at least as strong as the cohesive forces of the silicone rubber itself.

Another object of this invention is to improve the adhesion of silicone rubbersto'various metals and siliceous surfaces, such as glass and ceramics.

A still further object of the invention is to permit organopolysiloxanes containing less than 0.2 mol per cent copolymer'ized mono-organepolysiloxane and which are convertible to the solid elastic state to be bonded easily and quickly to metals, glass, ceramics, synthetic plastic surfaces, etc., so as to obtain a bonding zone highly resistant to deterioration at elevated tempera tures and capable of remaining flexible at very in my copending application, Serial No. 77,Q 4;5 filed February 17, 1949, now U. S. Patent/No. 2,601,337, and" assigned to same assignee as the present invention, there is disclosed and claimed methods for improving the adhesion of various orgariopoly'siloxanes' to different types of surfaces by first priming the surface with a disilane cor'-' respondingto the general formula (R)1iSi2(X) 6-1: Where R is a inonovalent hydrocarbon radical, X is ah'alog'en and n is an integer equal to from 1 to 4, prior to applying the organopolysiloxane to thesur'face. Although it has-been found that the usual heat cur'able' organopolysiloxanes prepared from liquid organopolysiloxanes condensed by condensing agents such as ferric chloride, etc, and using fillers such as titanium dioxide, lithopone,-etc., adhere satisfactorily to these various surfaces, it has been found unexpectedly that if the amount of copolyinerized mono organo siloxane goes below 0.2 mo1 per cent, the organo polysiloxane convertibletd acured, solid, elastic state, becomes more difiicult to adhere to various surfaces by means of the aforementioned disilanes as priming agents.- a W When silica aerogel is used as" a'filler' in con nection with orgahopolysiloxanes containing less than 0.2 mol per cent copolymerized mono organopolysiloxane, the silica aerogel appears to have the property of combining with the organopolysiloxane, apparently through some residual valence, to give a product which has better tensile strength and tear resistance than similar prod ucts of organopolysiloxanes wherein the filler is,

for example, titanium dioxide,--iron oxide, etc. These improved properties which are believed to be due to r'emrcireabuity of the crganoioolySiloxane by silica aerogel, appear to be specific to that filler and the above-mentionedconvertible organopolysiloxanes, which can be obtained by condensing organopolys'ilexanes having a monoorganosiloxane content below 0.2 mol per cent with various condensing agentsofwh-ich alkaline condensing agents, e. g. alkali=metal hydroxides, for instance, potassium hydroxide, sodium hy-' droxide,-etc-,, are especially suitable. Because of the improved'physical properties described above-,-

it has been found desirable to employ this silica aerogel-filled s ili conerubber in many applications. in adhering to solid surfaces such filled organol polysiloxanes or other such organopolysiloxanes containing less than 0.2 mol per cent copolymerized mono-organopolysilo'xane using other fillers, whether of the reinforcible or non-reinforcible type.

However, difficulty has-been encountered.

. 3 My invention is particularly adaptable for obviating this difficulty encountered in adhering such filled silicone rubbers to various surfaces, for example, in cases where molding is done around metal inserts or where it is attempted to mold gaskets of silica aerogel-filled (or other fillers) silicone rubbers to metallic backings or glass cloth backings, etc.

In accordance with my invention I have discovcred that I am able to effect adhesion of heatcurable organopolysiloxanes containing less than 0.2 mol per cent copolymerized mono-organopolysiloxane to various solid surfaces by first prim-v ing the surface with a hydrolyzable organo-silicate of the formula described above. Thereafter by effecting hydrolysis of the silicate either in situ or by external means, it will be found that on application of the convertible, e. g., heat-curable, organopolysiloxane, for example, the silica aerogel-filled silicone rubber, good adhesion takes a place and the contiguous surfaces can be molded under heat and pressure to convert the organopolysiloxane to the heat-cured, infusible, insoluble, solid, elastic state to give bonds which in many cases are stronger than the filled silicone rubbers themselves.

In the specification and in the claims, for brevity, the convertible organopolysilox anes, which may be viscous masses or gummy solids (depending on the state of condensation), will hereinafter A,

be referred to as "convertible organopolysiloxanes or more specifically as convertible methylpolysiloxanes. Although convertible organopolysiloxanes with which the present invention is concerned are now well known in the art, for I tober 11, 1949, or in Krieble et al. patent, 2,457,688

issued December 28,1948, all the foregoing patents being assigned to the same assignee as the present invent1on. It will, of course, be understood by those skilled in the art that other convertible organopolysiloxanes containing the same or diiierent silicon-bonded organic substituents (e. g., methyl, ethyl, propyl, phenyl, tolyl, xylyl, benzyl, phenylethyl, naphthyl, chlorophenyl, both methyl and phenyl, etc., radicals), connected to the silicon atoms by carbon-silicon linkages, may be employed without departing from the scope of this invention. The particular convertible organopolysiloxane used is not critical for adhesion purposes so long as it comes within the description above and is advantageously obtained from a condensation product preferably using an alkaline condensing agent, e. g., potassium hydroxide, etc.

The particular organosilicates coming within the general formula:

may, of course, be varied depending on the designation of R and R in the formula. Thus, for

example, B may be methyl, ethyl, propyl, iso-- propyl, butyl, amyl, isoamyl, octyl, iso-octylt.

decyl, dodecyl, halogenated alkyls, e. g. betachloroethyl, etc., radicals. R may be the same as R including halogenated derivatives of alkyl groups, as, for example, the chlorinated, bromi-- nated, fluorinated, etc., radicals, and the number of such halogens on the alkyl group may, of course," be varied, for example, from 1 to 4 or more. In addition, R may include alkoxy and aryloxy groups corresponding to the general formula:

where Z is, for instance, an alkyl group of the same class as described above for R, or additionally Z may be an aryl, aralkyl, and alkaryl radical, for example, phenyl, tolyl, xylyl, benzyl, phenylethyl, naphthyl, anthracyl, biphenyl, etc., radicals, as well as various halogenated derivatives of these aryl, aralkyl and alkaryl radicals, attached to the silicon atom through the medium of an oxygen atom. Thus, the halogens. for example, chlorine, bromine, etc, may be attached in any position in the alkyl group or in the aryl group and may comprises any number of halogens. When halogen is attached to an alkyl group, either in the R or R radical, it is preferable that the halogen should not be attached to the alpha carbon atom, due to the lower stability of such substituted alkyl groups.

I prefer to use organosilicates corresponding to the general formula:

where R is an alkyl group :as defined above. It

has been found that although aryl, for instance,

phenyl groups, or substituted aryl groups, will give excellent bonding immediately after the press cure, there is some deterioration of the bond with further heat aging which is not encountered in connection with the use of the alkyl silicates. In addition, the bond obtained using organosilicates containing aryl groups is not as satisfactory on glass, for example, as is the case when one employs the alkyl silicates.

The fact that these particular organosilicates \vere'effective for adhering convertible organopolysiloxanes to the various surfaces was entirely unexpected and in no way could have been pre dicted since it was found that similar composi-- tions of matter, for example, hydrolyzed silicic acid, dialkyldialkoxysilanes (e. g., dimethyldipropoxysilane) and trialkylalkoxysilanes were in effective in effecting bonding of the above-described convertible organopolysiloxanes to various surfaces. Even the use of organohalogenosilanes, for example, the use of methyltrichlorosilane or phenyltrichlorosilane was also ineffec-- -This hydrolysis operation may be effected in a variety of ways. For example, when one uses ethyl silicate corresponding to the formula hydrolysis of this material when applied to the surface to which it is desired to adhere the silioughly with water. The uncured silicone rubber compound, employed in Example 1 and more particularly-described above, was then'molded to the surface, again using light pressure (about 25-50 p. s. i.) for 10 minutes at 125 C. On removing from the mold and cooling, the bond was found to be fully developed and on subsequent heat aging in an oven for 1 hour at 150 C. and thereafter for 24 hours at 250 C., the bond continued to be stronger than-the cured silicone rubber itself.

Example 3 In this example, a mixture was prepared composed of 95%, by weight, tetraethylorthosilicate and by weight, of a polyorganohalogenopolysiloxane, specifically a polymet'nylchloropolysiloxane, more particularly disclosed and claimed in Sauer Patent 2,421,653 issued June 3, 1947, and assigned to the same assignee as the present invention. This mixture was applied to a cleaned steel surface similarly as was done in Examples 1 and 2, and thereafter the silica aerogel-filled dimethyl silicone gum was applied and molded in the same way as described above to give a bond showing a shear strength of about 700 p. s. i. Application of the same primer and molding of the same filled silicone rubber to othersurfaces such as cleaned copper and aluminum resulted in the same good bond.

When the primer in Example 3 was applied to glass, it was found preferable to add anhydrous .FeCl: in a small amount (about 0.25%) to the ethylorth'osilicate in place of the polymethylchloropolysiloxane. When a .glass surface was primed with this latter mixture of the Feclz and the ethyl ortho'silicate, and the same filled heatv curable methylpolysiloxane applied and molded to the treated surface, a good bond was obtained 250C. as described above. If this latter heat aging operation was conducted without resorting to priorroom'temperature cooling, it was found that the bond obtained after the final heat aging was inferior to the bond obtained when this cooling to room temperature took place.

Example 4 In this example the same ingredients and procedure were employed as in Example 2 with the exception that instead of tetraethylcrthosilicate, v -a similar amount of methyltripropoxysilane was used. The bond obtained in this case was satisfactory and even when heat-aged at elevated temperatures, it showed no evidence of deterioration but rather the bond appeared to be stronger than the rest of the'molded silicone rubber.

I p v Erample 5 In this example tetraethylorthosilicate was applied to a cleaned steel surface. Thereafter the surface was exposed to hydrogen chloride fumes,

to effect hydrolysis of the surface. The treated surface was then rinsed thoroughly with water to remove any tracesof residual 1101 or other contaminants and a sample of the heat-curable silicone gum containing the silica aerogel and benzoyl peroxide described in Example 1 was applied and molded in the same manner as described in the aforementioned Example 1. At the end of the first molding cycle .the bond was found, to

8 be satisfactoryand'continued to be at least as strong and in some cases stronger than the rest of the molded sample even when heat-aged at elevated temperatures of the order of 250 C. for 24 hours. I

Example 6 In this example, steel surfaces which had previously been substantially cleaned of contaminants and oxide formations were treated with various organosilicates coming within the scope of the generalformula found in column 1. These compounds included beta-chloroethylorthosilicate, t-butoxytriethoxysilane, t-amyloxytriethoxysilane, di-t-amyloxydiethoxysilane, cli-n-butoxydiethoxysilane, n-butoxytriethoxysilane, 2- methoxyethylorthosilicate, (CHaOCzHsO) 4Sil di-t-butoxydiethoxysilane, methyltributoxysilane, inethyltripropoxysilane, methyltriisopropoxysilane, di-t-butoxydiphenoxysilane, orthochlorophenylorthosilicate. Each of the organosilicates containing about 0.25%, by weight, anhydrous FeCla, based on the weight of the silicate, was applied tothe cleaned steel surface, and the surface permitted to stand in the air for about 12 hours to permit the moisture in the air to efiect hydrolysis of the silicate film in combination with the FeCls. Thereafter, each surface was rinsed with water to remove traces of residual HCl, and finally dried. To these primed surfaces there was applied the same filled heat-curable lnethylpolysilcxane employed in Examples 1 and 2 and the total assemblies molded using the same conditions as described in the aforementioned Example 1. At the end of the final heat treatment for 2s hours at 250 C., it was found that in each case (with the exception of the sample using dit-butoxydiphenoxysilane which showed a good bond after nitial cure but did not heat-age as well) a strong bond was obtained wherein the bond was at least as strong as the rest of the molded siliconerubber,and in many cases even stronger than the latter.

It will, of course, be understood by those skilled in the art that organosilicates other than those employed in the foregoing examples as well as other concentrations of the organosilicates and the hydrolysis-inducing materials required to effect hydrolysis of the organosilicates may also be employed without departing from the scope of the invention. Variations in concentration of the hydrolysis-inducing agent may depend on such factors as organosilicate used, solid surface to which adhesion is desired, hydrolysis-inducing catalyst employed, etc. It will also be apparent that I may employ other fillers (e. g., diatoms.-

ceous earth, titanium dioxide, lithopone, iron oxide, etc.) and convertible organcpolysiloxanes of the type described previously herein and also in Hyde Patent 2,490,357 issued December 6, 1949, and in MarsdenPa-tent 2,521,528 issued Septemher 5, 1950, the latter patent being assigned to the same assignee. In addition, the particular heat-convertible organopolysiloxane (which may be in a highly viscous, gummy state) reinforcible by silica aerogel, besides having been condensed by means of potassium hydroxide may have been condensed by other condensing agents, examples of which have been given previously.

Finally; instead of using a polymeric diorganosiloxane, as, for example, the polymeric dimethyl siloxane, containing about 2.0 organic, e. g., methyl, groups per silicon atom, organopolysiloxanes containing up to at most 0.2 mol percent copolymerized mono-organosiloxane, for example, co-

polymerized monomethyl siloxane, may also be used in the present instance. Generally, I prefer that the organopolysiloxane from which the heatcurable organopolysiloxane is prepared, contain about 1.998 to 2.0 inclusive, especially two, organic groups, for example, methyl groups, per silicon atom, and that more than 98 per cent, e. g., 99.8 per cent of the silicon atom in the polysiloxane contain two silicon-bonded organic groups, for instance, alkyl groups or mixtures of alkyl and aryl groups, for example, methyl groups, methyl and aryl groups, etc.

In connection with effecting adhesion of the convertible organopolysiloxanes, I have found that t-butoxytriethoxysilanewas particularly effective in adhering silicone rubber to magnesium. The use of this particular organosilicate gave stronger bonds than when other organosilicates were employed. Good .bonding to magnesium was obtained, however, using ethyl silicate with higher concentrations (a g. 1.5 to 2 per cent) .of hydrolysis-inducing catalysts, e. g., FeCla, etc.

My invention is equally applicable for adhering the covertible organopolysiloxanes to other glass surfaces as, for example, to glass tape, glass fibers, glass fiber sheets, etc. In the latter instance, glass cloth made from glass fibers was primed with .a mixture comprising tetraethylorthosilicate and a small amount of anhydrous FeCls in the manner described above in the foregoing examples, and thereafter a heat-curable organopolysiloxane filled with silica aerogel was adhered satisfactorily employing the technique and ingredients described in the foregoing examples. The bond realized in this case was so strong that after heat-curing, attempts to pull the cured silicone rubber from the glass backing resulted in tearing of the glass'fibers themselves indicating the bond was stronger than the silicone rubber.

My invention is applicable to almost all metal surfaces and is not specific as regards the particular metal to which adherence may be desired. In this respect it difiers from the techniques described and claimed in my foregoing copend-ing application, Serial No. 77,045, which are specific to most metallic and ceramic or siliceous surfaces other than copper.

The present invention is useful in adhering silicone rubbers to various metal surfaces as well as to various siliceous, for example, glass or ceramic surfaces. It can be used to bond silicone rubber to magnesium window frames or to any other type of metallic window frame where it is desired to obtain a surface resistant to cold and heat, as well as to deterioration .by the elements. In addition, electrical conductors, for example, copper conductors, can be passed through a priming solution of the particular organosilicate employed and thereafter insulated, for example, by extru- 'larly described in my aforementioned copending application. In this connection my invention is particularly adaptable for sealing the casings containing anodes and cathodes found in electrical discharge devices.

Finally, my invention has eminent utility in .molding heat-curable silicone rubberof the type described herein around steel inserts toget a good bond to the steel. Heretofore, attempts to use all kinds of priming agents were entirely unsatis factory because most of the time it was found that there was little if any bond induced between the insert and the heat-curable organopolysiloxane. It was therefore essential that a new process had to be developed for adhering the particular silicone rubbers reinforcible by silica aerogel described herein since prior methods for adhering this particular type of filled silicone rubber were unsatisfactory.

What I claim as new and desire to secure by Letters Patent of the United States is:

1. The process for improving the adhesion to a solid surface of an organopolysiloxane convertible to the solid, elastic state and containing less than 0.2 mol per cent .copolymerized mono-organesiloxane, which process comprises treating the said surface with a composition comprising an organosilicate corresponding to the general formula;

R l no-s i-n" where .R is a member selected from the class consisting of alkyl groups and halogen-substituted alkyl groups, and R is a member selected from 1 the class consisting of alkyl, aryl, aralkyl, alkaryl,

- silicate, and thereafter applying the aforesaid organopolysiloxane to the treated surface and heat-treating the latter until a solid, elastic product isobtained.

3. The process for improving the adhesion to a .solid surface of an organopolysiloxane convertible to the solid, elastic state and contaim'n-gless than 0.2 mol per cent copolymerized mono-organosiloxane, which process comprises treating the said surface prior to applying the organopolysiloxane with a composition comprising t-butoxytriethoxysilane, and thereafter applying the aforesaid organopolysiloxane to the surface and heat-treating the latter until a solid, elastic prod-- uct is obtained.

A. The process for improving the adhesion to a solid surface of an organopolysiloxane convertible to the solid, elastic state and containing less than 0.2 mol per cent copolymerized monoorganosiloxane, which process comprises treating the said surface prior to applying the organopolysiloxane with a composition comprising methyl triethoxysilane, and thereafter applying the aforesaid organopolysiloxane to the surface and heat-treating the latter until a solid, elastic product is obtained.

,5. The process for improving the adhesion to a solid surface of an organopolysiloxane convertible to the solid, elastic state and containing less than 0.2 mol per cent copolymerized monoorganosiloxane, which process comprises treating 11 the said surface prior to applying the organopolye siloxane with a composition comprising beta= chloroethylorthosilicate, and thereafter applying the aforesaid organopolysiloxane tothe surface and heat-treating the latter until a solid, elastic product is obtained.

6. The process for improving the adhesion to a solid surface of an organopolysiloxane convertible to the solid, elastic state and containing less than 0.2 mol per cent copolymerized mono-organosiloxane, Which process comprises treating the said surface prior to applying the organopoly siloxane with a composition comprising di-tamyloxydiethoxysilane, and thereafter applying the aforesaid organopolysiloxane to the surface and heat-treating the latter until a solid, elastic product is obtained.

7. The process for improving the adhesion to a solid surface of a methylpolysiloxane heatcurable to the solid, elastic state and containing less than 0.2 mol per cent copolymerized monomethylsiloxane, which process comprises treating the said surface withtetraethyl silicate, and thereafter applying the aforesaid methylpolysiloXane to the surface and heat-treating the latter until a solid, elastic product is obtained.

8. The process for improving the adhesion to a solid surface of a methylpolysiloxane heat-cur able to the solid, elastic state and containing less than 0.2 mol per cent copolymerized monomethylsiloxane, which process comprises treating the said surface with t-butoxytriethoxysilane, and

thereafter applying the aforesaid methylpolysil-- oxane to the surface and heat-treating the latter until a solid, elastic product is obtained.

9. The process for improving the adhesion to a solid surface of a methylpolysiloxane heatcurable to the solid, elastic state and containing less than 0.2 mol per cent copolymerized monomethylsiloxane, which process comprises treating the said surface with methyl triethoxysilane, and

thereafter applying the aforesaid methylpolysiloxane to the surface and heat-treating the latter until a solid, elastic product is obtained.

10. The process for improving the adhesion-to M a solid surface of a methylpolysiloxane heat-curable to the solid, elastic state and containing less than 0.2 mol per cent copolymerized monomethylsiloxane, which process comprises treating the said surface with beta-chloroethylorthosilicate.

.treating the latter until a solid, elastic product is obtained.

12. The process as in claim 7 wherein the ethyl silicate used to treat the surface contains a small amount of an anhydrous iron halide incorporated therein.

13. The process as in claim 8 wherein the tbutoxytriethoxysilane used to treat the surface contains a small amount of an anhydrous iron halide incorporated therein.

14. The process as in claim 9 wherein the methyl triethoxysilane used to treat the surface contains a small amount of an anhydrous iron halide incorporated therein.

r 15. The process asin claim 10 wherein the betachloroethylorthosilicate used to treat the surface contains a small amount of an iron halide incorporated therein.

16. The process as in claim 11 wherein the di-tamyloxydiethoxysilane used to treat the surface contains a small amount of an anhydrous iron halide incorporated therein.

17. An article of manufacture comprising (1) a solid surface primed with a hydrolyzed composition comprising an organosilicate corresponding to the general formula:

where R is a member selected from the class consisting of alkyl groups and halogen-substituted alkyl groups and R, represents a member selected from the class consisting of alkyl, aryl, aralkyl, alkaryl, alkoxy, aryloxy groups, and halogenated derivatives of the aforesaid alkyl, aryl, aralkyl, .alkaryl, alkoxy and aryloxy groups, and (2) an adherent layer comprising a solid, elastic organopolysiloxane containing less than 0.2 mol per cent co polymerized mono organosiloxane bonded firmly to the primed solid surface.

18. An article of manufacture comprising (1) a metallic surface primed with a hydrolyzed composition comprising (a) ethyl orthosilicate and (b) an anhydrous iron halide, and (2) an adherent layer comprising a solid, elastic methylpolysiloxane containing less than 0.2 mol per cent co-polymerized monomethylsilcxane;

19. An article of manufacture comprising -(l) a magnesium surface primed with a hydrolyzed composition comprising (a) ethyl orthosilicate and (b) a small amount of an anhydrous iron halide, and (2) an adherent layer comprising a solid, elastic methylpolysiloxane containing less than 0.2 mol per cent co-polymerized monomethylsiloxane bonded firmly to the primed magnesium surface.

20. An article of manufacture comprising (1) a glass surface primed with a hydrolyzed composition comprising (a) ethyl orthosilicate and (b) a small amount of an anhydrous iron halide, and (2) an adherent layer comprising a solid, elastic methylpolysiloxane containing less than 0.2 mol per cent copolymerized monometh- 'ylsiloxane bonded firmly to t he primed glass comprising (a) ethyl orthosilicate and (b) .a

small amount up to at most 1%, by weight, of

anhydrous ferric chloride, and (2) an adherent layer comprising a heat-cured solid, elastic methylpolysiloxane containing less than 0.2 mol per cent copolymerized monomethylsiloxane bonded firmly to the primed glass cloth surface.

23. A composition of matter consisting solely of (1) an organosilicate corresponding to the general formula:

groups, and (2) 9, small amount of an iron halide.

24. A composition of matter consisting solely of (1) ethyl orthosilicate and (2) anhydrous ferric chloride.

25. A composition of matter consisting solely of (l) t-butoxytriethoxysilane and (2) a small amount of ferric chloride.

26. A composition of matter consisting solely of (1) methyl triethoxysilane and. (2) a small amount of anhydrous ferric chloride.

2'7. A composition of matter consisting solely of (1) beta-chloroethylorthosilicate and (2) a small amount of anhydrous ferric chloride.

28. A composition of matter consisting solely of (1) di-t-amyloxydiethoxysilane and (2) small amount of anhydrous ferric chloride.

29. The hydrolyzed product of the composition defined in claim 23.

30. The hydrolyzed product of the composition defined in claim 24.

31. The hydrolyzed product of the composition defined in claim 25.

32. The process for obtaining a solid surface to which is tenaciously adhered a cured, solid, elastic organopolysiloxane, which process comprises (1) applying to a solid surface, a filled 14 organopolysiloxane convertible to the cured, solid, elastic state and containing less than 0.2 mol per cent of copolymerized mono-organosiloxane, in which filled organopolysiloxane there is incorporated a curing agent, the said solid surface containing thereon, prior to application of the filled organopolysiloxane, a composition comprising a hydrolysis product of an organosilicate corresponding to the general formula:

where R is a member selected from the class consisting of alkyl groups and halogen-substituted alkyl groups, and R. is a member selected from the class consisting of alkyl, aryl, aralkyl, alkaryl, alkoxy, aryloxy groups, and halogenated derivatives of the aforesaid alkyl, aryl, aralkyl, alkaryl, alkoxy, and aryloxy groups, and (2) thereafter heating the applied organopolysiloxane at an elevated temperature until a cured, solid, elastic product is obtained, and a tenacious bond is attained between the solid surface and the cured organopolysiloxane.

ROBERT SMITH-JOHANNSEN.

References Cited in the file of this patent UNITED STATES PATENTS Number Name Date 2,389,477 Wright et a1. Nov. 20, 1945 2,436,304 Johannson Feb. 17, 1948 2,452,416 Wright Oct. 26, 1948 2,464,231 Hersh Mar. 15, 1949 2,485,928 Servais Oct. 25, 1949 2,502,286 Sowa Mar. 28, 1950 OTHER REFERENCES Sauer, Journal of Amer. Chem. Society, 68, pp. 138-139 (1946). 

1. THE PROCESS FOR IMPROVING THE ADHESION TO A SOLID SURFACE OF AN ORGANOPOLYSILOZANE CONVERTIBLE TO THE SOLID, ELASTIC STATE AND CONTAINING LESS THAN 0.2 MOL PER CENT COPOLYMERIZED MONO-ORGANOSILOXANE, WHICH PROCESS COMPRISES TREATING THE SAID SURFACE WITH A COMPOSITION COMPRISING AN ORGANOSILICATE CORRESPONDING TO THE GENERAL FORMULA: 